fix(galaxy-collection): make sure that releaseTimestamp is returned correctly

[jamietanna]

Changes

As noted in #35936, we've been collecting this data, but hadn't been
correctly returning it when enriching the release.

Although we could also collect this data from the rawDetailedVersion,
we can start by wiring in the basicRelease's releaseTimestamp, if
present.

Context

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The public repository: https://github.com/khung/galaxy-collection-timestamp-repro